Controller methods and views

https://docs.asp.net/en/latest/tutorials/first-mvc-app/controller-methods-views.html

We have a good start to the movie app, but the presentation is not ideal. We don’t want to see the time (12:00:00 AM in the image below) and ReleaseDate should be two words.

Open the Models/Movie.cs file and add the highlighted lines shown below:

public class Movie
{
    public int ID { get; set; }
    public string Title { get; set; }

    [Display(Name = "Release Date")]
    [DataType(DataType.Date)]
    public DateTime ReleaseDate { get; set; }
    public string Genre { get; set; }
    public decimal Price { get; set; }
}

using System.ComponentModel.DataAnnotations;

We’ll cover DataAnnotations in the next tutorial.

The Display attribute specifies what to display for the name of a field (in this case “Release Date” instead of “ReleaseDate”).

The DataType attribute specifies the type of the data, in this case it’s a date, so the time information stored in the field is not displayed.

Browse to the Movies controller and hold the mouse pointer over an Edit link to see the target URL.

The Edit, Details, and Delete links are generated by the MVC Core Anchor Tag Helper in theViews/Movies/Index.cshtml file.

<td>
                <a asp-action="Edit" asp-route-id="@item.ID">Edit</a> |
                <a asp-action="Details" asp-route-id="@item.ID">Details</a> |
                <a asp-action="Delete" asp-route-id="@item.ID">Delete</a>
            </td>

Tag Helpers enable server-side code to participate in creating and rendering HTML elements in Razor files.

In the code above, the AnchorTagHelper dynamically generates the HTML href attribute value from the controller action method and route id.

You use View Source from your favorite browser or use the F12 tools to examine the generated markup.

The F12 tools are shown below.

Chrome浏览器，在界面上右键，检查：然后会弹出一个浏览界面，左上角的指针图标，单击之后，移动到页面上，会随着移动而展开html

Recall the format for routing set in the Startup.cs file.

 app.UseMvc(routes =>
            {
                routes.MapRoute(
                    name: "default",
                    template: "{controller=Home}/{action=Index}/{id?}");
            });

ASP.NET Core translates http://localhost:1234/Movies/Edit/4 into

a request to the Edit action method of the Movies controller with the parameter ID of 4.

(Controller methods are also known as action methods.)

Tag Helpers are one of the most popular new features in ASP.NET Core. See Additional resources for more information.

Open the Movies controller and examine the two Edit action methods:

// GET: Movies/Edit/5
        public async Task<IActionResult> Edit(int? id)
        {
            if (id == null)
            {
                return NotFound();
            }

            var movie = await _context.Movie.SingleOrDefaultAsync(m => m.ID == id);
            if (movie == null)
            {
                return NotFound();
            }
            return View(movie);
        }

        // POST: Movies/Edit/5
        // To protect from overposting attacks, please enable the specific properties you want to bind to, for
        // more details see http://go.microsoft.com/fwlink/?LinkId=317598.
        [HttpPost]
        [ValidateAntiForgeryToken]
        public async Task<IActionResult> Edit(int id, [Bind("ID,Genre,Price,ReleaseDate,Title")] Movie movie)
        {
            if (id != movie.ID)
            {
                return NotFound();
            }

            if (ModelState.IsValid)
            {
                try
                {
                    _context.Update(movie);
                    await _context.SaveChangesAsync();
                }
                catch (DbUpdateConcurrencyException)
                {
                    if (!MovieExists(movie.ID))
                    {
                        return NotFound();
                    }
                    else
                    {
                        throw;
                    }
                }
                return RedirectToAction("Index");
            }
            return View(movie);
        }

The [Bind] attribute is one way to protect against over-posting.

You should only include properties in the [Bind] attribute that you want to change.

See Protect your controller from over-posting for more information.

ViewModels provide an alternative approach to prevent over-posting.

Notice the second Edit action method is preceded by the [HttpPost] attribute.

[HttpPost]
[ValidateAntiForgeryToken]
public async Task<IActionResult> Edit(int id, [Bind("ID,Genre,Price,ReleaseDate,Title")] Movie movie)
{
    if (id != movie.ID)
    {
        return NotFound();
    }

    if (ModelState.IsValid)
    {
        try
        {
            _context.Update(movie);
            await _context.SaveChangesAsync();
        }
        catch (DbUpdateConcurrencyException)
        {
            if (!MovieExists(movie.ID))
            {
                return NotFound();
            }
            else
            {
                throw;
            }
        }
        return RedirectToAction("Index");
    }
    return View(movie);
}

The HttpPostAttribute attribute specifies that this Edit method can be invoked only for POST requests.

You could apply the [HttpGet] attribute to the first edit method, but that’s not necessary because [HttpGet] is the default.

The ValidateAntiForgeryTokenAttribute attribute is used to prevent forgery of a request and is paired up with an anti-forgery token generated in the edit view file (Views/Movies/Edit.cshtml).

The edit view file generates the anti-forgery token with the Form Tag Helper.

<form asp-action="Edit">

The Form Tag Helper generates a hidden anti-forgery token that must match the[ValidateAntiForgeryToken] generated anti-forgery token in the Edit method of the Movies controller.

For more information, see